JP5803516B2 - Fuel cell device - Google Patents

Description

  The present invention relates to a fuel cell device including a reformer that generates fuel gas to be supplied to a fuel cell.

  A reformer is incorporated in a solid oxide fuel cell (SOFC) apparatus. The reformer reforms a to-be-reformed gas (for example, city gas), which is a supplied raw material gas, with a reforming catalyst to generate a fuel gas, and supplies the fuel gas to a fuel cell. Since the operating temperature of the fuel cell in the power generation process is as high as 600 ° C. to 800 ° C., the fuel gas supplied to the fuel cell needs to be a fuel gas heated to a predetermined temperature or higher. For this reason, the reformer is disposed above the combustion section that burns the mixed gas of the fuel gas and the oxidant gas that has not contributed to the power generation discharged from the fuel battery cell, and the combustion heat of the mixed gas and the fuel It is heated by radiant heat from the battery cell.

  In the reformer described in Patent Document 1, the reforming section filled with the reforming catalyst includes a flow path extending meandering in the short direction of the reformer from the vaporization section to the supply pipe. When the gas to be reformed is supplied to the flow path, it is utilized for the reforming reaction from the reforming catalyst on the upstream side of the flow path. The reforming catalyst used deteriorates due to, for example, carbon deposition, and the reforming catalyst further downstream than the catalyst deteriorated along with the deterioration is sequentially used for the reforming reaction. The fuel gas generated by the reforming reaction is supplied to the fuel battery cell through the supply pipe. At this time, the fuel gas in the flow path is heated by the fuel in the fuel chamber.

JP 2010-195625 A

  In general, an endothermic reaction occurs in the reforming catalyst due to the reforming reaction, so that the temperature of the reformed gas decreases at the position of the reforming catalyst where the endothermic reaction has occurred. As described above, as the reforming catalyst deteriorates, the reforming catalyst used for the reforming reaction moves to the downstream side, so that there is not enough distance to the downstream end of the flow path. The fuel gas after being reformed by the reforming catalyst is supplied to the fuel cell without being sufficiently heated, and the operating temperature of the fuel cell is lowered. Therefore, it is necessary to replace the reforming catalyst with a margin that does not lower the operating temperature, and the downstream reforming catalyst cannot be used effectively.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell device that can be effectively used up to a downstream catalyst.

In order to achieve the above object, according to the present invention,
In a fuel cell device including a fuel cell that generates power with fuel gas and oxidant gas,
A fuel gas flow path formed inside the fuel cell and allowing the fuel gas to flow from the bottom to the top of the fuel cell;
An oxidant gas flow path that is formed outside the fuel battery cell and flows the oxidant gas from the lower part to the upper part of the fuel battery cell;
A combustion section that is disposed above the fuel cell and that mixes and burns the fuel gas discharged from the fuel gas flow path and the oxidant gas discharged from the oxidant gas flow path;
A reformer having a reforming channel disposed above the fuel battery cell and filled with a catalyst that reforms the supplied reformed gas into the fuel gas by heat from the combustion section. ,
The reforming channel is
An upstream channel extending from the upstream end of the reforming channel without contacting the side wall of the reformer;
A pair of downstream flow paths branched from the downstream end of the upstream flow path and extending meandering to the downstream end of the reforming flow path,
Each of the downstream flow paths is disposed outside the first serpentine flow path, the first meander flow path extending from the downstream end of the upstream flow path without coming into contact with the side wall of the reformer, and There is provided a fuel cell device having a second serpentine channel extending in contact with a side wall of the reformer from a downstream end of the first serpentine channel to a downstream end of the reforming channel.

  In such a fuel cell device, when the gas to be reformed is supplied to the reformer, the gas to be reformed flows through the reforming channel in the reformer and comes into contact with the catalyst in the reforming channel. It is reformed to gas. At this time, the reformer is heated by the combustion heat from the combustion of the fuel gas and the oxidant gas in the combustion section and the radiant heat from the fuel cell. In the reforming channel, only the second serpentine channel disposed outside the first serpentine channel on the inner side of the downstream channel extends along the side wall of the reformer. Therefore, combustion heat is transmitted from the side wall to the reformed gas in the second meandering channel on the outermost side of the downstream channel. On the other hand, it is difficult for combustion heat to be transmitted to the upstream flow path and the first serpentine flow path that do not contact the side wall of the reformer. As a result, the reformed gas can be heated more efficiently in the second meandering channel than in the upstream channel or the first meandering channel. Even if the catalyst in the second meandering channel is used to reform the reformed gas, the reformed gas can be sufficiently heated in the second meandering channel. That is, the heating characteristics can be improved in the second meandering flow path. In this way, even the downstream catalyst can be effectively used.

  According to the fuel cell device of the present invention, it is preferable that the downstream flow path meanders along the long side of the reformer. Thus, the outermost second meandering channel of the downstream side channels extends while contacting the side wall on the long side of the reformer, so that the gas to be reformed in the second meandering channel is heated for a long time. The As a result, the efficiency of heating by combustion in the combustion section can be increased.

  In the fuel cell device according to the present invention, the second meandering channel of the downstream channel extends in contact with both the long side wall and the short side wall of the reformer. Is preferred. Thus, the second meandering channel extends while being in contact with both the long side wall and the short side wall of the reformer, so that the gas to be reformed in the second meandering channel is heated for a longer time. . As a result, the efficiency of heating by combustion in the combustion section can be further increased.

  Further, according to the fuel cell device of the present invention, the cross-sectional area of the downstream flow path orthogonal to the flow direction of the reformed gas is the upstream flow path orthogonal to the flow direction of the reformed gas. It is preferable to set it smaller than the cross-sectional area of Due to the difference in the cross-sectional areas of the flow paths, the flow speed of the gas to be reformed in the downstream flow path can be set larger than the flow speed of the gas to be reformed in the upstream flow path. Thus, the gas to be reformed in the downstream channel collides with the catalyst at a higher flow rate than the gas to be reformed in the upstream channel, so that the gas to be reformed in the downstream channel compared to the upstream channel. The reformed gas can be stirred more greatly. As a result, in the downstream channel, the thermal diffusion effect can be enhanced in the direction orthogonal to the flow of the reformed gas compared to the upstream channel. Heat can be efficiently transferred by the reformed gas.

  As described above, according to the present invention, it is possible to provide a fuel cell device that can be effectively used up to the downstream catalyst.

It is a perspective view which shows the external appearance of the fuel cell module of the fuel cell apparatus which concerns on one Embodiment of this invention. It is sectional drawing of the fuel cell module of FIG. It is sectional drawing of the fuel cell module of FIG. It is a perspective view which shows the state which removed some outer plates from the casing of FIG. FIG. 3 is a schematic diagram corresponding to FIG. 2, and is a schematic diagram illustrating flows of an oxidant gas and a combustion gas. FIG. 4 is a schematic diagram corresponding to FIG. 3, and is a schematic diagram illustrating flows of an oxidant gas and a combustion gas. It is a fragmentary sectional view showing a fuel cell unit. It is a perspective view which shows the structure of a fuel cell stack. It is a perspective view which shows the external appearance of the reformer which concerns on one Example. FIG. 10 is a perspective view showing a state in which the upper wall of the reformer of FIG. 9 is removed. It is a top view which shows the internal structure of a reformer. FIG. 12 is a cross-sectional view taken along line 12-12 of FIG. It is a top view which shows the internal structure of another Example. It is a top view which shows the internal structure of a comparative example. It is a graph which verifies the effect of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same constituent elements in the drawings will be denoted by the same reference numerals as much as possible, and redundant description will be omitted. FIG. 1 is a perspective view showing an appearance of a fuel cell module 2 of a fuel cell device according to an embodiment of the present invention. The fuel cell module 2 constitutes a part of a solid oxide fuel cell (SOFC) device. That is, the fuel cell device includes a fuel cell module 2 and an auxiliary unit (not shown).

  In FIG. 1, the height direction of the fuel cell module 2 is the y-axis direction. The x-axis and z-axis are defined along a plane orthogonal to the y-axis, the direction along the short direction (width direction) of the fuel cell module 2 is defined as the x-axis direction, and the longitudinal direction (long) of the fuel cell module 2 is defined. The direction along the vertical direction is the z-axis direction. The x-axis, y-axis, and z-axis described in FIG. 2 and thereafter are based on the x-axis, y-axis, and z-axis in FIG. Further, the direction along the negative direction of the z axis is the A direction, and the direction along the positive direction of the x axis is the B direction.

  The fuel cell module 2 includes a casing 56 that houses fuel cells (details will be described later), and a heat exchanger 22 that is provided on the upper portion of the casing 56. The casing 56 is formed in a rectangular parallelepiped shape, for example. The heat exchanger 22 is disposed on the upper surface of the casing 56. A fuel cell assembly, which will be described later, is disposed in the casing 56. A reformed gas supply pipe 60 and a water supply pipe 62 are connected to the casing 56. On the other hand, a power generation air introduction pipe 74 and a combustion gas discharge pipe 82 are connected to the heat exchanger 22.

  The to-be-reformed gas supply pipe 60 is a pipe line that supplies a to-be-reformed gas for reforming such as city gas into the casing 56. The water supply pipe 62 is a pipe line that supplies water used when steam reforming the gas to be reformed to the inside of the casing 56. The power generation air introduction pipe 74 is a conduit for supplying power generation air (oxidant gas) for causing a power generation reaction with the fuel gas generated by the reforming. The combustion gas discharge pipe 82 is a pipe that discharges the combustion gas generated as a result of burning the remaining fuel gas and oxidant gas that did not contribute to power generation to the outside.

  Next, the internal structure of the fuel cell module 2 of the fuel cell device according to the present invention will be described with reference to FIGS. FIG. 2 is a cross-sectional view of the fuel cell module 2 cut along a cutting plane parallel to the xy plane of FIG. FIG. 3 is a cross-sectional view of the fuel cell module 2 cut along a cutting plane parallel to the yz plane of FIG. 4 is a perspective view showing a state where a part of the casing 56 is removed from the fuel cell module 2 shown in FIG.

  As shown in FIGS. 2 to 4, the casing 56 covers the entire fuel cell assembly 12 of the fuel cell module 2. The fuel cell assembly 12 is formed of an assembly of fuel cell units 16 arranged in parallel to each other. As shown in FIG. 5, the fuel cell assembly 12 has a substantially rectangular parallelepiped shape that is longer in the A direction than in the B direction as a whole, and an upper surface that extends parallel to the xz plane along the lower surface of the reformer 20; A lower surface extending parallel to the xz plane along the upper surface of the fuel gas tank 68, a pair of long side surfaces extending parallel to the yz plane, and a pair of short side surfaces extending parallel to the xy plane are provided.

  In the case of the present embodiment, an evaporating mixer for evaporating water supplied from the water supply pipe 62 is provided inside the reformer 20. The evaporative mixer is heated by the combustion gas burned in the combustion section 18 to be described later, and converts water into water vapor, and also mixes this water vapor, reformed gas (city gas, etc.), and air. Is. The reformed gas supply pipe 60 and the water supply pipe 62 are both led to the interior of the casing 56 and then connected to the reformer 20. More specifically, as shown in FIG. 3, the to-be-reformed gas supply pipe 60 and the water supply pipe 62 are connected to the right end in the figure, which is the upstream end of the reformer 20.

  The reformer 20 is disposed further above the combustion unit 18 formed above the fuel cell assembly 12. Therefore, the reformer 20 is heated by the combustion heat of the remaining fuel gas and oxidant gas that has not contributed to power generation after the power generation reaction, and serves as an evaporative mixer and as a reformer that causes the reforming reaction. And is configured to play a role. The upper end of the fuel supply pipe 66 is connected to the downstream end (the left end in FIG. 3) of the reformer 20. A lower end side 66 a (see FIG. 2) of the fuel supply pipe 66 is disposed so as to enter the fuel gas tank 68. Details of the reformer 20 will be described later.

  As shown in FIGS. 3 and 4, the fuel gas tank 68 is provided directly below the fuel cell assembly 12. A plurality of small holes (not shown) are formed along the longitudinal direction (A direction) on the outer periphery of the lower end side 66 a of the fuel supply pipe 66 inserted into the fuel gas tank 68. The fuel gas generated by the reformer 20 is uniformly supplied in the longitudinal direction into the fuel gas tank 68 through the plurality of small holes (not shown). The fuel gas supplied to the fuel gas tank 68 is supplied into a fuel gas flow path (details will be described later) inside each fuel cell unit 16 constituting the fuel cell assembly 12, and the fuel cell unit 16 The interior of the interior rises from the lower portion toward the upper portion and reaches the combustion section 18.

  Next, a structure for supplying power generation air into the fuel cell module 2 will be described with reference to FIGS. 5 and 6 in addition to FIGS. FIG. 5 is a schematic diagram corresponding to FIG. 2 and shows the flow of the oxidant gas and the combustion gas. FIG. 6 is a schematic diagram corresponding to FIG. 3, and similarly shows the flow of the oxidant gas and the combustion gas. As shown in these drawings, a heat exchanger 22 is disposed above the reformer 20. In the heat exchanger 22, a plurality of combustion gas pipes 70 and a power generation air passage 72 formed around the combustion gas pipes 70 are provided.

  The aforementioned power generation air introduction pipe 74 is attached to one end side (the right end in FIG. 3) of the upper surface of the heat exchanger 22. The oxidant gas is introduced into the heat exchanger 22 from the power generation air flow rate adjustment unit (not shown) by the power generation air introduction pipe 74. A pair of outlet ports 76 a and 76 a for the power generation air flow path 72 are formed on the other end side (the left end in FIG. 3) on the upper side of the heat exchanger 22. Each of the outlet ports 76a is connected to a communication channel 76. Further, as shown in FIG. 2, power generation air supply passages 77 are formed on the outer sides of the casing 56 in the width direction.

  Therefore, the oxidant gas is supplied to the power generation air supply path 77 from the outlet port 72 a of the power generation air flow path 72 and the communication flow path 76. The power generation air supply path 77 is formed along the longitudinal direction of the fuel cell assembly 12. Further, in order to blow out the oxidant gas toward each fuel cell unit 16 of the fuel cell assembly 12 in the power generation chamber 10 at a position corresponding to the lower side and the lower side of the fuel cell assembly 12. A plurality of outlets 78a and 78b are formed. The oxidant gas blown out from these air outlets 78 a and 78 b flows from the lower part to the upper part of the fuel cell unit 16 along the outside of each fuel cell unit 16. That is, the oxidant gas flow path 79 is formed between the fuel cell units 16 and 16.

  Next, a structure for discharging combustion gas generated by combustion of fuel gas and oxidant gas will be described. The combustion gas generated above the fuel cell unit 16 rises in the combustion section 18 and reaches the rectifying plate 21. The rectifying plate 21 is provided with an opening 21a, and combustion gas is guided into the opening 21a. The combustion gas that has passed through the opening 21 a reaches the other end side of the heat exchanger 22. In the heat exchanger 22, a plurality of combustion gas pipes 70 are provided for discharging combustion gas generated by combustion of fuel gas and oxidant gas in the combustion unit 18. A combustion gas discharge pipe 82 is connected to the downstream end side of these combustion gas pipes 70, and the combustion gas is discharged to the outside through the discharge pipe 82.

  Next, the fuel cell unit 16 will be described with reference to FIG. FIG. 7 is a partial cross-sectional view showing the fuel cell unit 16. As shown in FIG. 7, the fuel cell unit 16 includes a fuel cell 84 and inner electrode terminals 86 respectively connected to the vertical ends of the fuel cell 84. The fuel cell 84 is a tubular structure extending in the vertical direction, and includes a cylindrical inner electrode layer 90 that forms a fuel gas flow path 88 therein, and a cylindrical outer electrode layer that extends concentrically with the inner electrode layer 90. 92, and an electrolyte layer 94 disposed between the inner electrode layer 90 and the outer electrode layer 92. The inner electrode layer 90 is a fuel electrode through which fuel gas passes and becomes a (−) electrode, while the outer electrode layer 92 is an air electrode in contact with air and becomes a (+) electrode.

  Since the inner electrode terminals 86 attached to the upper end and the lower end of the fuel cell unit 16 have the same structure, the inner electrode terminal 86 attached to the upper end will be specifically described here. The upper part 90 a of the inner electrode layer 90 includes an outer peripheral surface 90 b and an upper end surface 90 c exposed to the electrolyte layer 94 and the outer electrode layer 92. The inner electrode terminal 86 is connected to the outer peripheral surface 90b of the inner electrode layer 90 through a conductive sealing material 96, and further directly contacts the upper end surface 90c of the inner electrode layer 90, whereby the inner electrode layer 90 is electrically connected. Connected. A fuel gas passage 98 communicating with the fuel gas passage 88 of the inner electrode layer 90 is formed at the center of the inner electrode terminal 86.

  The inner electrode layer 90 includes, for example, a mixture of Ni and zirconia doped with at least one selected from rare earth elements such as Ca, Y, and Sc, and Ni and ceria doped with at least one selected from rare earth elements. The mixture is formed of at least one of Ni and a mixture of lanthanum garade doped with at least one selected from Sr, Mg, Co, Fe, and Cu.

  The electrolyte layer 94 is, for example, zirconia doped with at least one selected from rare earth elements such as Y and Sc, ceria doped with at least one selected from rare earth elements, lanthanum gallate doped with at least one selected from Sr and Mg, Formed from at least one of the following.

  The outer electrode layer 92 includes, for example, lanthanum manganite doped with at least one selected from Sr and Ca, lanthanum ferrite doped with at least one selected from Sr, Co, Ni and Cu, Sr, Fe, Ni and Cu. It is formed from at least one of lanthanum cobaltite doped with at least one selected from the group consisting of silver and silver.

  Next, the fuel cell stack 14 will be described with reference to FIG. FIG. 8 is a perspective view showing the fuel cell stack 14. As shown in FIG. 8, the fuel cell stack 14 includes 16 fuel cell units 16, and the lower end and the upper end of each fuel cell unit 16 have a ceramic fuel gas tank upper plate 68a and an upper support, respectively. It is supported by the plate 100. The fuel gas tank upper plate 68a and the upper support plate 100 are formed with through holes through which the inner electrode terminal 86 can pass.

  Further, a current collector 102 and an external terminal 104 are attached to the fuel cell unit 16. The current collector 102 electrically connects the inner electrode terminal 86 attached to the inner electrode layer 90 that is a fuel electrode and the outer peripheral surface of the outer electrode layer 92 that is the air electrode of the adjacent fuel cell unit 16. Connecting. Further, external terminals 104 are connected to the inner electrode terminals 86 at the upper and lower ends of the two fuel cell units 16 located at the ends of the fuel cell stack 14. These external terminals 104 are connected to the external terminals 104 of the fuel cell unit 16 at the end of the adjacent fuel cell stack 14, and all 160 fuel cell units 16 are connected in series.

  Next, the reformer 20 will be described with reference to FIGS. FIG. 9 is a perspective view showing the appearance of the reformer 20. FIG. 10 is a perspective view with the upper wall removed from the reformer 20 shown in FIG. FIG. 11 is a plan view showing the internal structure of the reformer 20 shown in FIG. 12 is a cross-sectional view taken along line 12-12 of FIG. In FIG. 10, the illustration of the catalyst is omitted.

  As shown in FIGS. 9 and 10, the reformer 20 includes a flat rectangular parallelepiped casing 25. The housing 25 has a pair of side walls 25a and 25b extending in parallel to each other in the short direction. The reformed gas supply pipe 60 and the water supply pipe 62 are connected to the side wall 25a at the upstream end of the reformer 20, and the fuel supply pipe 66 is connected to the side wall 25b at the downstream end of the reformer 20. Has been. The housing 25 further includes a pair of side walls 25c and 25d extending in parallel with each other in the longitudinal direction, and an upper wall 25e and a bottom wall 25f extending in parallel with each other continuously from the side walls 25a to 25d. .

  As is clear from FIGS. 10 and 11, the reformer 20 includes an evaporative mixing unit 26 formed on the side wall 25a side, that is, the upstream side, and a reforming unit 27 formed on the side wall 25b side, that is, the downstream side. I have. The evaporating and mixing unit 26 and the reforming unit 27 are partitioned from each other by a single partition wall 28 extending between the side walls 25c and 25d, and a plurality of vent holes 29 are formed in the partition wall 28. In the evaporative mixing unit 26, the water supplied from the water supply pipe 62 is vaporized into water vapor. This water vapor is mixed with the reformed gas supplied from the reformed gas supply pipe 60. In the evaporating and mixing unit 26, various meandering channels are formed by a plurality of ribs.

  The reforming portion 27 is connected to the partition wall 28 at the upstream end, and extends in parallel and linearly along the side walls 25c and 25d. The reforming portion 27 surrounds the ribs 30 and 30 from the outside. And a reforming flow path 32 formed by the rib 31. The ribs 31 are linear ribs 33 that extend in parallel to the ribs 30 while facing the outward faces of the ribs 30 on the inward faces, and the inward faces at the downstream ends of the ribs 30 and 30 continuously to the straight ribs 33 and 33. And the curved ribs 34 facing each other. The outward surface of the curved rib 34 faces the upstream end of the fuel supply pipe 66.

  The reforming channel 32 is formed by the ribs 30, 30 and connected to the vent hole 29 at the upstream end, and the upstream channel 35 is connected to the downstream end of the upstream channel 35 at the upstream end. And a pair of downstream flow paths 36 and 36 that branch in opposite directions from the downstream end of the path 35. The downstream channel 36 extends while meandering to the downstream end of the reforming channel 32. In the present embodiment, the downstream flow path 36 meanders along the long side of the casing 25 of the reformer 20. Each downstream flow path 36 includes an inner flow path 37 formed between the rib 30 and the straight rib 33, and an outer flow path formed between the linear rib 33 and the side wall 25 c or the side wall 25 d of the reformer 20. And a path 38. The downstream ends of the outer channels 38, 38 join between the side wall 25 b of the reformer 20 and the curved rib 34. In the present embodiment, the downstream flow path 36 includes one inner flow path 37 and one outer flow path 38, but may include a plurality of inner flow paths 37. That is, the downstream flow path 36 may meander twice or more times.

  As is apparent from FIGS. 10 to 12, combustion heat from the combustion unit 18 is transmitted to the upstream flow path 35 and the downstream flow path 36 through the bottom wall 25 f. Only the outer channel 38 is in contact with the side walls 25b, 25c and 25d of the housing 25, and combustion heat is transmitted to the outer channel 38 via the side walls 25b, 25c and 25d. On the other hand, in the present embodiment, the outer channel 38 surrounds the upstream channel 35 and the inner channel 37, and the upstream channel 35 and the inner channel 37 are formed on the side walls 25 a to 25 d of the housing 25. Since they are not in contact with each other, the combustion heat from the side walls 25 a to 25 d is hardly transmitted into the upstream flow path 35 and the inner flow path 37.

As is apparent from FIG. 11, the reforming flow path 32 is filled with the catalyst 39 from the upstream end to the downstream end. As the catalyst 39, an Al ₂ O ₃ (alumina) sphere surface supporting Ni (nickel) or an alumina sphere surface supporting Ru (ruthenium) is appropriately used. The reformed gas flowing through the reforming flow path 32 from the upstream end toward the downstream end is reformed by contact with the catalyst 39 after being mixed with reforming air or water. The fuel gas generated by the reforming flows into the fuel supply pipe 66. Thereafter, as described above, the fuel gas is supplied to each fuel cell unit 16.

  As shown in FIG. 12, the cross-sectional area of the upstream flow path 35 perpendicular to the flow direction of the reformed gas is set larger than the cross-sectional area of the inner flow path 37 perpendicular to the flow direction of the reformed gas. Is done. Similarly, the cross-sectional area of the inner flow path 37 is set larger than the cross-sectional area of the outer flow path 38 orthogonal to the flow direction of the reformed gas. That is, the cross-sectional area gradually decreases from the upstream end to the downstream end of the reforming channel 32. As a result, in the reforming flow channel 32, the flow rate of the reformed gas in the inner flow channel 37 is set larger than the flow rate of the reformed gas in the upstream flow channel 35. Further, the flow rate of the gas to be reformed in the outer flow path 38 is set larger than the flow rate of the gas to be reformed in the inner flow path 37.

  Next, the operation of the fuel cell module 2 will be described. When the fuel cell module 2 is started, a mixed gas in which the gas to be reformed and the reforming air is mixed is supplied to the combustion unit 18 via the reformer 20, and the oxidant gas is supplied to the power generation air. It is supplied via the introduction pipe 74. In the combustion unit 18, the mixed gas and the oxidant gas ignited by a spark plug (not shown) are combusted, and the combustion heat due to the combustion is evaporated through the bottom wall 28f of the casing 25 of the reformer 20 and the side walls 25a-25d. 26 and the reforming unit 27 are heated. At the same time, the combustion gas generated by the combustion passes through the combustion gas pipe 70 in the heat exchanger 22 to warm the oxidant gas in the power generation air flow path 72 of the heat exchanger 22.

At this time, in the reformer 20, the above-mentioned mixed gas comes into contact with the catalyst 39 in the reforming unit 27, whereby the partial oxidation reforming reaction POX shown in the following formula (1) proceeds.
C _m H _n + xO ₂ → bCO + cH ₂ (1)
Fuel gas is generated by this partial oxidation reforming reaction POX. Since the partial oxidation reforming reaction POX is an exothermic reaction, the generated fuel gas is heated by the exothermic reaction and its temperature rises. This fuel gas is supplied from the fuel gas tank 68 to the fuel chamber 18 via the fuel cell assembly 12. As a result, the fuel cell assembly 12 is heated from above and below by the combustion unit 18 and the fuel gas tank 68.

Thereafter, for example, depending on the temperature of the fuel cell assembly 12, water is supplied to the reformer 20 in addition to the mixed gas in which the gas to be reformed and air are mixed. Since the reformer 20 has already been heated to a high temperature, water is mixed with the mixed gas in the state of water vapor in the mixing chamber. At this time, in the reformer 20, the mixed gas comes into contact with the catalyst 39 in the reforming unit 27, whereby the above-mentioned partial oxidation reforming reaction POX and the steam reforming reaction SR described later are used in combination. ATR progresses.
C _m H _n + xO ₂ + yH ₂ O → bCO + cH ₂ (2)

Thereafter, by stopping the supply of air and increasing the supply of water, the steam reforming reaction SR proceeds in the reformer 20 by bringing the mixed gas into contact with the catalyst 39.
C _m H _n + xH ₂ O → bCO + cH ₂ (3)
In the steam reforming reaction SR, an endothermic reaction occurs when the high-temperature reformed gas and steam come into contact with the surface of the catalyst 39. At this stage, since the fuel cell assembly 12 is heated to a sufficiently high temperature, even if an endothermic reaction proceeds, the fuel cell assembly 12 does not cause a significant temperature drop. Combustion continues in the combustion section 18.

  As described above, when the fuel cell module 2 is started, the partial oxidation reforming reaction POX, the autothermal reforming reaction ATR, and the steam reforming reaction SR proceed in sequence, so that the temperature of the fuel cell assembly 12 reaches a high temperature. After rising, power generation processing is started in the fuel cell assembly 12. During the power generation process, the steam reforming reaction SR with high reforming efficiency is continued in the reformer 20. At this time, carbon is deposited on the surface of the catalyst 39 by the reforming reaction, and the surface area of the catalyst 39 is reduced by the carbon deposition. Further, the active points of the catalyst 39 are lost as impurities and the like contained in the reformed gas adhere to the surface of the catalyst 39. Thus, the catalyst 39 is deteriorated. As the catalyst 39 deteriorates, the position of the catalyst 39 that causes the reforming reaction moves downstream.

  In the reformer 20, only the outer channel 38 in the downstream channel 36 extends in contact with the side walls 25b, 25c, and 25d of the casing 25 of the reformer 20, so that the reformer 20 passes through the side walls 25b, 25c, and the side wall 25d. Combustion heat is transmitted from the combustion section 18 to the reformed gas in the outer flow path 38. On the other hand, since the combustion heat is not easily transmitted to the upstream flow path 35 and the inner flow path 37 that do not contact the side walls 25b and 25c and the side wall 25d of the reformer 20, In comparison, the reformed gas can be heated more efficiently in the outer flow path 38. In the reforming channel 32, the heating characteristics can be further improved on the downstream side compared to the upstream side. As a result, even if the catalyst 39 in the outer flow path 38 is used for reforming the reformed gas, the reformed gas can be sufficiently heated in the outer flow path 38.

  Moreover, the flow velocity of the reformed gas increases as the cross-sectional area decreases stepwise from the upstream flow path 35 toward the inner flow path 37 and the outer flow path 38. As a result, the gas to be reformed comes into contact with the catalyst 39 at a higher flow rate as it goes downstream, so that the gas to be reformed is in the inner flow path 37 compared to the upstream flow path 35 and similarly in the inner flow path 37. Compared to the above, the outer channel 38 is more greatly stirred. Thus, compared with the upstream flow path 35 and the inner flow path 37, the outer flow path 38 can enhance the thermal diffusion effect in the direction orthogonal to the flow direction of the reformed gas. As a result, the heating characteristics can be further improved on the downstream side compared to the upstream side of the reforming channel 32. In addition, since the outer flow paths 38 and 37 merge at the downstream end, the reformed gas can be further agitated at the merge point.

  As described above, the catalyst 39 deteriorates as the reforming reaction is repeated. As a result, the position of the catalyst 39 that causes the reforming reaction moves downstream. However, according to the present invention, since the heating characteristics can be further improved on the downstream side compared to the upstream side, even if the position of the catalyst 39 causing the reforming reaction moves to the downstream side, the downstream side flow is improved. Compared with the upstream flow path 35, the combustion heat from the fuel chamber 18 is more efficiently transmitted to the reformed gas through the housing 25 in the path 36. Therefore, in the present invention, even the catalyst 39 on the downstream side of the reforming channel 32 can be used effectively. As a result, the number of times of replacing the catalyst 39 can be reduced.

  Next, the effect of the present invention was verified. In the verification, the reformer 20 described above was used as the first embodiment of the present invention, while the reformer 20 having the same cross-sectional area in all the flow paths was assumed as the second embodiment. Here, in the reformer 20 according to the second embodiment, as shown in FIG. 13, the flow of the reformed gas in the upstream flow path 35, the inner flow path 37, and the outer flow path 38 of the reformer 20. All the cross-sectional areas of the cross section perpendicular to the direction were set equal. In the second embodiment, the upstream flow path 35 of the reformer 20 is divided into two flow paths having the same cross-sectional area. On the other hand, in the reformer according to the comparative example, as shown in FIG. 14, in the reforming channel 32 of the second embodiment, the upstream channel 35 and the inner channel 37 are in contact with the side wall 25b. Configured.

  At this time, the temperature T in the flow path from the upstream end to the downstream end of the reforming flow path 32 was measured in the reformers according to the first and second examples and the reformer according to the comparative example. FIG. 15 is a graph showing the relationship between the distance d defined along the reforming channel 32 from the upstream end of the reforming channel 32 and the temperature T at each distance d. As shown in FIG. 15, in the first embodiment, the reformed gas in the outer flow path 38 can receive the combustion heat through the side wall 25c or the side wall 25d and the side wall 25b. The characteristic (slope of temperature rise) is greatly increased. On the other hand, in the comparative example, the heating characteristic does not change so much. Therefore, it can be seen that the heating characteristics can be improved by the fact that only the outer flow path 38 is in contact with the side wall and that the cross-sectional area decreases toward the downstream side. On the other hand, in the second embodiment, since the cross-sectional areas are set to be equal, the heating characteristics are improved in the outer flow path 38 compared to the comparative example, although the heating characteristics are inferior to the first embodiment. I understand that

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In other words, those specific examples that have been appropriately modified by those skilled in the art are also included in the scope of the present invention as long as they have the characteristics of the present invention. For example, the elements included in each of the specific examples described above and their arrangement, materials, conditions, shapes, sizes, and the like are not limited to those illustrated, and can be changed as appropriate. Moreover, each element with which each embodiment mentioned above is provided can be combined as long as technically possible, and the combination of these is also included in the scope of the present invention as long as it includes the features of the present invention.

20 reformer 32 reforming channel 35 upstream channel 36 downstream channel 37 inner channel (first serpentine channel)
38 Outer channel (second serpentine channel)
39 Catalyst 79 Oxidant gas flow path 84 Fuel cell 88 Fuel gas flow path

Claims (3)

In a fuel cell device including a fuel cell that generates power with fuel gas and oxidant gas,
A fuel gas flow path formed inside the fuel cell and allowing the fuel gas to flow from the bottom to the top of the fuel cell;
An oxidant gas flow path that is formed outside the fuel battery cell and flows the oxidant gas from the lower part to the upper part of the fuel battery cell;
A combustion section that is disposed above the fuel cell and that mixes and burns the fuel gas discharged from the fuel gas flow path and the oxidant gas discharged from the oxidant gas flow path;
Filling a housing of rectangular parallelepiped shape that will be disposed above the fuel cells, a catalyst used for reforming the fuel gas to be reformed gas supplied is formed inside the casing by the heat from the combustion unit A reformer having a reformed flow path,
The reforming channel is
An upstream flow path extending in the longitudinal direction of the casing without contacting the side wall of the casing from the upstream end of the reforming flow path;
A pair of downstream flow paths branched from the downstream end of the upstream flow path and extending meandering to the downstream end of the reforming flow path,
Each of the downstream flow paths is more than a first serpentine flow path extending in the longitudinal direction of the casing without contacting a side wall of the casing from the downstream end of the upstream flow path, and the first serpentine flow path A second meandering channel disposed outside and extending from a downstream end of the first serpentine channel to a downstream end of the reforming channel in contact with the side walls in the longitudinal and short sides of the casing. A fuel cell device.   The reformer is
  A pair of first ribs facing each other and extending in the longitudinal direction of the housing, the pair of first ribs defining the upstream flow path therebetween,
  A pair of second ribs disposed outside the pair of first ribs and defining the first serpentine flow path between the pair of first ribs;
  A curved rib that is continuous with the pair of second ribs, faces the downstream end of the pair of first ribs, and connects the downstream end of the upstream channel and the upstream end of the first serpentine channel And having
  2. The fuel cell device according to claim 1, wherein the curved rib is curved so that an outward surface of the curved rib faces a side wall in a short direction of the casing. A cross-sectional area of the downstream flow path orthogonal to the flow direction of the reformed gas is set to be smaller than a cross-sectional area of the upstream flow path orthogonal to the flow direction of the reformed gas. The fuel cell device according to claim 1 or 2 .

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